Saturday, 4 October 2014

Autumn excursions...

We have encountered bottlenose dolphins four times so far this season in their traditional coastal niche. We saw then twice in the space of five days during July (10th and 15th) in typical groups of around 12-15 animals performing sporadic behaviour splitting off into smaller groups and occasional bow riding and general associations. 
August again produced two encounters with the first one being on the 19th when we had just arrived back from a Whalewatch Explorer at 1630 in Tobermory and as we were getting Sula Beag ready for the next trip we noticed an animal surface roll at the entrance to the harbour so we continued to watch on as a couple of bottlenose dolphins surfaced again showing that large back, tall dorsal fin and fine spray as they exhale. The animals continued to work their way into the harbour as we watched from Sula Beag alongside the pontoon and a growing audience observing from the shore. The animals stayed in the vicinity and we managed to see them for the evenings Ecocruz and enjoyed spectacular views along with capturing some photo ID shots of individuals. 

Bottlenose dolphin close surface

On the 26th August another special encounter for this season occurred when Sula Beag was surrounded by a superpod of over a thousand dolphins! Dolphin splash could be seen panning from one horizon to the other making the sea state look choppy on a windless day. An abundance of behaviour was observed which included splinter pods driving at the surface chasing shoals of fish. Other groups were performing strong interactions which included bow riding, wake riding and social connections when we drifted with the engines off. If all aboard did not already know it was a special encounter at the time they did when skipper James announced it was easily the largest number of dolphins he had observed in a lifetime of covering Hebridean waters!

Common dolphins associating with the underwater camara. Photo courtesy of James Fairbairns
As we made our way into the month of September we welcomed a wonderful settled high pressure spell of weather lasting for over two weeks which provided increased opportunities on our marine excursions. Regular common dolphin sightings continued and personal relations with two individual minke whales was had during the month. One of the animals had a distinct white spot on the trailing edge of its dorsal fin and we encountered the animal on the 11th, 16th and 17th of September. The minke was seen in the same concentrated area on every sighting which shows strong site fidelity.
The other minke whale seen in September was identifiable through sound and the distinct noise it made when it surfaced. The animal was nicknamed 'Horse' due to the relating sound and you can watch a video here. We had two sightings of the animal in the space of three days with the first record off the island of Coll's coastline before being recorded five miles to the east off Ardnamurchan peninsula! Skipper James said that it is the first whale he has known in these waters to be identified by the distinct sound of its surface blow.

We also managed some strong photo records of the minkes dorsal fin and back which was less unique in features compared to the other whale recorded.

Minke whale with the white spot in its trailing edge of its dorsal fin

Minke whale close surface roll
On the 17th September on a four hour Wildlife Adventure we were just making our way out of the Sound of Mull and working along a strong tide line full of lion's mane jellyfish when Andy shouted sunfish! Everyone looked off the bow as an ocean sunfish was coming towards us only metres away! The sea was flat calm like a millpond and as Skipper James cut the engines, the animal swam right underneath us providing wonderful clear views. That was our third record of sunfish this season with the other two records being in the month of August.
Ocean sunfish are the largest bony fish in the world and grow from a larva stage of 2.5mm to up to three metres! That is the equivalent of a human baby growing to the size of three Titanic vessels! They also produce around three million eggs a season!

Of course we can not forget the engineers of all marine life in the ocean, the plankton! Samples were very abundant throughout September with a large variation of zoo plankton collected on a daily basis. Some of the species were copepods, arrow worms, cladocera, crab larva, lobster larva, starfish larva, jellyfish larva, segmented worms, bristle worms and phtoplankon including diatoms and dinoflagellates. The on-board microscope aims to enthuse and inspire guests about the facinating microscopic world.

Copepod under the microscope, thanks to Andy Tait for the photo.
On 13th September during a Wildlife Adventure we discovered a large piece of polystyrene floating out at sea about a metre squared so the crew and skipper managed to retrieve it as this sort of marine litter can be hugely threatening to ecosystems through species consumption and we try and 'do our bit' of tidying up on every cruise. Polystyrene is very dangerous to marine life because it floats on the surface and also easily breaks down into smaller pieces. It is the most common substance worldwide to be found in a sea birds stomach.

A sad and happy occasion, photo by Rona Mcann
Marine litter in general is an increasing threat and researchers predict that on average 1km squared of sea will contain 13,000 pieces of plastics / micro plastics, and concentrated tidal areas will have millions. These tidal convergences make certain food source more abundant as well, so it creates vital feeding grounds for species like minke whales and in turn increases marine litter consumption and entanglement risks. Marine litter is entirely a man made problem which means we are also in complete control, and can reduce or stop the highly threatening risk to our oceans.

Ewan

Head Guide

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